Cytoskeletet

The cytoskeleton, known as cytoskeletet in Swedish, is a dynamic network of protein filaments that extends throughout the cytoplasm. It provides structural support, helps define cell shape, organizes internal components, and drives movement. It also coordinates intracellular transport and signaling, enabling the cell to respond to environmental and mechanical cues. The cytoskeleton consists of three main filament systems: microfilaments (actin filaments), intermediate filaments, and microtubules. Actin filaments are thin and highly adaptable, involved in shape changes, surface projections, and contractile structures. Microtubules are stiff, hollow tubes that organize the cell’s interior and serve as tracks for motor proteins to shuttle vesicles and chromosomes. Intermediate filaments are diverse and provide mechanical resilience under stress.

The networks are regulated by a set of accessory proteins that nucleate, stabilize, sever, crosslink, and motorize the filaments. Arp2/3 and formins promote actin filament growth, while spectrin and filamin crosslink networks. The microtubule core is organized by the gamma-tubulin ring complex at microtubule-organizing centers, commonly the centrosome in animal cells. Motor proteins such as myosin move along actin, whereas kinesin and dynein travel along microtubules to transport cargo and drive movement.

In cells, the cytoskeleton supports the cortex, organizes organelles, forms the mitotic spindle during division, and enables locomotion through structures like lamellipodia and filopodia. Cilia and flagella rely on bundled microtubules for propulsion. The cytoskeleton is highly dynamic, remodeling continuously in response to signals and mechanical cues. Defects in cytoskeletal components are linked to diseases such as neurodegenerative disorders and cancer metastasis.